Otbivnoe

@_functionBuilder
struct SubviewsBuilder {
    static func buildBlock(_ views: UIView...) -> [UIView] {
        return views
    }
}

extension UIView {
    func addSubviews(@SubviewsBuilder _ subviews: () -> [UIView]) -> UIView {
        subviews().forEach { addSubview($0) }

Otbivnoe

@dynamicMemberLookup
struct Person {
    subscript(dynamicMember member: String) -> String {
        let properties = ["name": "Nikita", "age": "24"]
        return properties[member, default: ""]
    }
}

print(Person().name) // Nikita

Otbivnoe

protocol ProtocolWithAssociatedType {
    associatedtype T
}

struct Test<T>: ProtocolWithAssociatedType {} // no compile error
struct Test: ProtocolWithAssociatedType {}    // error: Type 'Test' does not conform to protocol 'ProtocolWithAssociatedType'

Otbivnoe

func printData(from keyPaths: KeyPath<[String: Any], Any?>...) {
    keyPaths.forEach { keyPath in
        print(dict[keyPath: keyPath])
    }
}

printData(from: \.name, \.age)

// Optional("Nikita")
// Optional(24)

Otbivnoe

@dynamicMemberLookup
protocol DictionaryDynamicLookup {
    associatedtype Key
    associatedtype Value
    subscript(key: Key) -> Value? { get }
}

extension DictionaryDynamicLookup where Key == String {
    subscript(dynamicMember member: String) -> Value? {
        return self[member]

Otbivnoe

extension UserDefaults {
    
    subscript<T: RawRepresentable>(key: String) -> T? {
        get {
            if let rawValue = value(forKey: key) as? T.RawValue {
                return T(rawValue: rawValue)
            }
            return nil
        }
        set {

Otbivnoe

enum AppTheme: Int {
    case light
    case dark
}

class SettingsService {

    var appTheme: AppTheme {
        get {
            if let rawValue: AppTheme.RawValue = UserDefaults.standard[#function], let theme = AppTheme(rawValue: rawValue) {

Otbivnoe

extension UserDefaults {

    subscript<T>(key: String) -> T? {
        get {
            return value(forKey: key) as? T
        }
        set {
            set(newValue, forKey: key)
        }
    }

Otbivnoe

class SettingsService {

    var isNotificationsEnabled: Bool {
        get {
            let isEnabled = UserDefaults.standard.value(forKey: #function) as? Bool
            return isEnabled ?? true
        }
        set {
            UserDefaults.standard.setValue(newValue, forKey: #function)
        }

Otbivnoe

class SettingsService {

    private enum Keys {
        static let isNotificationsEnabled = "isNotificationsEnabled"
    }

    var isNotificationsEnabled: Bool {
        get {
            let isEnabled = UserDefaults.standard.value(forKey: Keys.isNotificationsEnabled) as? Bool
            return isEnabled ?? true